1. Field of the Invention
The present invention relates to the direct distribution of pay TV content, and particularly relates to methods and apparatuses to establish a two-way communication link between a broadcast TV set and an IPTV server.
2. Background
Digital television sets are typically designed to display free-to-air digital content broadcasted over cable or terrestrial networks. The digital broadcast signals include multiple channels modulated at different RF frequencies, which are distributed within a frequency range. Each RF channel carries multiple programs, such as video, audio, and other data, multiplexed together in a MPEG transport stream. The digital television set expects some standardized program information data to be available within one or more transport stream to create a global channel map.
When connected to pay TV services, a set-top box is typically added in front of the digital television set for receiving the transmission, selecting a channel and decrypting the signal. The set-top box thus provides a navigation function for selecting a channel within the received signal. The set-top box can also provide a security function for decrypting the received signal. For example, the set-top box can be a part of a conditional access (CA) system for verifying the entitlements of the subscriber before removing the encryption.
Alternatively, modern HDTV (High Definition Television) receivers can have an interface to plug a renewable Conditional Access Module (CAM), capable of removing the conditional access encryption based on the subscription level and to re-encrypt for a locally secured transmission back to the HDTV. Such an architecture based on open standards, as for example the DVB Common Interface standard with the CI+ extension in Europe, or the OpenCable standard in North America, allows for the design of truly generic television sets that work with different CAMs, which can be selectively attached and detached. The generic HDTV receiver includes one or more RF tuners, one or more CAM interfaces and the right resources for decoding, rendering the content, but also optionally for content storage and/or export. The CAM interface is positioned in between the receiving function (RF Tuner) and the processing function (decoder, recorder, rendered, exporter) of the HDTV receiver. The HDTV receivers must support the standardized DRM system of the CAM so it can cryptographically pair with the CAM and descrambled the content returned by the CAM.
Further and depending on the HDTV receiver implementation, there could be one CAM per RF tuner or one for multiple RF tuners. The CAM has the ability to generate subscription and diagnostics messages that will be presented to the user by the HDTV.
In addition, IPTV (Internet Protocol Television) can provide an alternative digital broadband distribution of the same video and data. Usually HDTV receivers don't support these services, as it required a two-way communication path with the IPTV server, combined with network specific navigation, streaming and security protocols.